Uses for health purposes

There are several reasons that people are interested in probiotics for health
purposes.

First, the world is full of microorganisms (including bacteria), and so are
people's bodies -- in and on the skin, in the gut, and in other orifices. Friendly
bacteria are vital to proper development of the immune system, to protection
against microorganisms that could cause disease, and to the digestion and
absorption of food and nutrients. Each person's mix of bacteria varies.
Interactions between a person and the microorganisms in his body, and among the
microorganisms themselves, can be crucial to the person's health and well-being.

This bacterial "balancing act" can be thrown off in two major ways:

1. By antibiotics, when they kill friendly bacteria in the gut along with
unfriendly bacteria. Some people use probiotics to try to offset side
effects from antibiotics like gas, cramping, or diarrhea. Similarly, some
use them to ease symptoms of lactose intolerance -- a condition in which the
gut lacks the enzyme needed to digest significant amounts of the major sugar
in milk, and which also causes gastrointestinal symptoms.

2. "Unfriendly" microorganisms such as disease-causing bacteria, yeasts,
fungi, and parasites can also upset the balance. Researchers are exploring
whether probiotics could halt these unfriendly agents in the first place
and/or suppress their growth and activity in conditions like:

Infection with Helicobacter pylori (H. pylori), a bacterium that causes most ulcers and many types of chronic stomach inflammation

Tooth decay and periodontal disease

Vaginal infections

Stomach and respiratory infections that children acquire in daycare

Skin infections

Another part of the interest in probiotics stems from the fact there are
cells in the digestive tract connected with the immune system. One theory is
that if you alter the microorganisms in a person's intestinal tract (as by
introducing probiotic bacteria), you can affect the immune system's defenses.